bombogenesis

The weather forecast for the US Northeast is dire, calling for a fierce late winter storm, with plenty of snow. Map from the Northeast Weather site on Facebook (link from Eleanor Houck, who lives in the Reading area in southeastern Pennsylvania, right in the red zone):

In some of the forecasts, Eleanor came across the colorful technical term bombogenesis, suggesting a “weather bomb”. New to her, and to me, but it’s been around for a while.

A powerhouse Nor’easter is poised to slam the region. Blizzard conditions, damaging winds, beach erosion and more among the multiple impacts to be felt from this rare system.

Folks, the setup doesn’t get any better than this for the development of a PARALYZING blizzard for the megalopolis I-95 corridor on N & W.

With a fresh injection of cold air in place over the region, all we need is moisture. and there will certainly be NO shortage of that with this system. It appears as though moisture from the Gulf of Mexico, the, Caribbean AND the Atlantic will all be streaming together to create a FIREHOSE directed right into a fresh injection of cold air sitting over our region.

I am anticipating a large and expansive area of 1-3′ (yes, FEET) of snow for millions living along the I-95 corridor and N&W suburbs from Philadelphia to Boston come late Wednesday afternoon as the low pushes off to the NE

Explosive cyclogenesis (also referred to as a weather bomb, meteorological bomb, explosive development, or bombogenesis) refers in a strict sense to a rapidly deepening extratropical cyclonic low-pressure area. To enter this category, the central pressure of a depression at 60° latitude is required to decrease by 24 mb (hPa) or more in 24 hours.

This is a predominantly maritime, cold-season (winter) event, but also occurs in continental settings.This process is the extratropical equivalent of the tropical rapid deepening.

In the 1940s and 50s meteorologists at the Bergen School of Meteorology [see below] began informally calling some storms that grew over the sea “bombs” because they developed with a ferocity rarely, if ever, seen over land.

By the 1970s the terms “explosive cyclogenesis” and even “meteorological bombs” were being used by MIT professor Fred Sanders (building on work from the 1950s by Tor Bergeron), who brought the term into common usage in a 1980 article in the Monthly Weather Review. In 1980, Sanders and his colleague John Gyakum defined a “bomb” as an extratropical cyclone that deepens by at least (24 sin φ/ sin 60˚)mb in 24 hours, where φ represents latitude in degrees. [Note that the technical definition, satandarized by Bergeron, is dependent on latitude. The drop of 24 millibars in 24 hours is the figure for 60° latitude. In North America, 60° N runs from Alaska on the west to Newfoundland and Labrador on the east. Philadelphia is roughly 40° N, so a somewhat smaller drop in air pressure is sufficient for cyclogenesis.]

The “Bergen School of Meteorology” is a school of thought which is the basis for much of modern weather forecasting.

… Much of the work was done at the Geophysical Institute, University of Bergen, in Bergen, Norway.

Cold, snowy events like the Northeast weather bomb (especially out of season) are not infrequently taken to constitute disproof of global warming (or climate change in general). But of course they’re nothing of the sort: while temperatures steadily rise on average, there’s still local weather. In fact, extreme weather events like the Northeast weather bomb might be part of the climate change package. From Wikipedia:

Global warming and climate change are terms for the observed century-scale rise in the average temperature of the Earth’s climate system and its related effects. Multiple lines of scientific evidence show that the climate system is warming. Many of the observed changes since the 1950s are unprecedented over tens to thousands of years.

… Future climate change and associated impacts will differ from region to region around the globe. Anticipated effects include warming global temperature, rising sea levels, changing precipitation, and expansion of deserts in the subtropics. Warming is expected to be greater over land than over the oceans and greatest in the Arctic, with the continuing retreat of glaciers, permafrost and sea ice. Other likely changes include more frequent extreme weather events including heat waves, droughts, heavy rainfall with floods and heavy snowfall; ocean acidification; and species extinctions due to shifting temperature regimes. Effects significant to humans include the threat to food security from decreasing crop yields and the abandonment of populated areas due to rising sea levels. Because the climate system has a large “inertia” and greenhouse gases will stay in the atmosphere for a long time, many of these effects will not only exist for decades or centuries, but will persist for tens of thousands of years.

Denialism persists too. Some denialists maintain that there’s been no change in global temperature, that all reports to this effect are propaganda fabricated by scientists anxious to establish their reputations and earn money from their work. More cagey denialists concede that global temperatures are indeed rising, but maintain that this change is just part of long-range natural shifts in global climate, shifts taking place on a geological time scale, and has nothing to do with human activity or with greenhouse gases like carbon dioxide and methane.

Even cagier denialists adopt a strategy refined in disputes over the dangers of smoking tobacco: that that facts are not in yet, the subject is very hard to study, there’s substantial disagreement as to the facts, and the matter needs further examination. Which brings us to the new head of the US Environmental Protection Agency, Scott Pruitt, the subject of much recent press, including a Politifact story on the 10th, “EPA head Scott Pruitt says carbon dioxide is not ‘primary contributor’ to global warming” by Lauren Carroll:

“Do you believe that it’s been proven that CO2 is the primary control knob for climate?” CNBC anchor Joe Kernen asked Pruitt in a March 9 interview.

“No, I think that measuring with precision human activity on the climate is something very challenging to do and there’s tremendous disagreement about the degree of impact,” Pruitt responded. “So no, I would not agree that it’s a primary contributor to the global warming that we see.”

“I would not agree that it’s a primary contributor” is significantly weaker than “I maintain that it’s not a primary contributor” (with negation on the assertion clause rather than the speech-act clause), and that in turn is significantly weaker than “I maintain that it’s not a contributor” (with no hedging on the degree of the contribution), and significantly weaker than the flat-out assertion “It’s not a contributor” — which is no doubt what Pruitt actually believes, but he wants to leave himsef a lot of wiggle room.